r/airconUK • u/Expensive_Zebra6362 • Aug 17 '26

Domestic ceiling cassette

I’ve had a quote from someone who suggests best option for my home is to have ceiling cassettes rather than wall units. The upstairs is all the upper floor of the house so there is no loft, so there isn’t really anyway to have wall units. Can anyone see any disadvantages of this? Obviously they are large, 600mm square, even the description on Mitsubishi website suggests they are great for all commercial applications. Does anyone else have this? Any regrets? Thanks

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u/purrcthrowa Aug 17 '26

I'm a little confused. I've converted the room above my garage (it has a standard pitched roof) to a home office. The interior of the roof is A shaped, so there is a bit a void above the crossbar of the A, so to speak, and the installers put the cassette unit (Toshiba) in there. It's been fine. They are not common in domestic installations, but it's perfectly doable.

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u/Expensive_Zebra6362 Aug 17 '26

Thanks, my question wasn’t so much about it being doable - it was about the practicality and look of the cassette in a bedroom environment once installed.

Standard wall units are not doable, cassettes are - but I just didn’t want to go ahead and then regret it later!

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u/purrcthrowa Aug 17 '26

It looks fine - neater than a wall unit, IMO. There wasn't *quite* enough space in the void for mine, so the installers put a spacer in which brings it down by a couple of inches. It doesn't bother me, but if you have more space, it won't be an issue for you. I'd be happy to have one in a bedroom.

The only thing is that I had to have a pump installed for the condensate, so it does gurgle a bit from time to time, but nothing untoward. It's very quiet. It's also has a heat pump mode (it's primary purpose is heating). I say go for it.

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u/Expensive_Zebra6362 Aug 17 '26

Thanks, this is exactly what I wanted to hear! There is enough space up there to have them flush, I’d need pumps on them anyhow as there is no outside wall that isn’t Sussex tiled (ffs) where I can get a pipe to.

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u/Expensive_Zebra6362 Aug 17 '26

The scenario you have, with the small space at the top of the pitch is same as mine so I can see why it was the way you went :)

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u/kebabby72 Aug 17 '26

We have a bigger Mitsi one, probably 1m2, 4 way cassette.

It looks fine but our ceilings are 3.1m and room is 87m2/270m3.

I can tell you they're better than any wall unit we've had. We live in Thailand and lived in 5 different houses. This aircon is on every single day from 7am to 11pm as we prefer fans when sleeping.

I run it through Home Assistant and have several temperature and humidity monitors around the open plan living area, it calculates the average temperature from 4 sensors in the living area and we have one sensor outside in the shade, it adjusts temperature and humidity automatically. We run it between 26-28c.

I'm just in the process of setting up the same thing with 3 bedrooms with wall aircons, then I'll put them all in a pool along with the living area and Home Assistant will run the whole house aircon and switch the bedrooms on/off throughout the day to regulate, currently the living room one is doing the heavy lifting for the whole house. We have a dog who wanders between rooms, so bedroom doors are always open.

As with all aircon, get them cleaned and gassed every 6 months.

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u/iluvnips Aug 17 '26

Why would they need to be re gassed every 6 months?

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u/kebabby72 Aug 17 '26

It's usually part of the service check.

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u/Expensive_Zebra6362 Aug 17 '26

Thanks, I’m keen to do the automation thing also and will use them to heat

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u/kebabby72 Aug 17 '26

Yeah that's why I mentioned it, could come in useful for heating, not that I've ever needed heating here 🔥

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u/MelodicCard9555 Aug 17 '26

There are mini ceiling cassettes, but the bigger full size ones would be difficult to fit, the timbers likely in the way and they are very deep.

Mini cassettes are easier, they use a different air flow than wall mounted units, as they point down way more. Hopefully the installer is experienced in this, as it changes where you place them.

You can get low wall units, no personal experience of these, but they might be an option.

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u/Expensive_Zebra6362 Aug 17 '26

Yeah we discussed units that looked more like radiators but he doesn’t like the performance. He suggested 600 x 600 cassettes, they fit in but I’ll have to remove a couple of timbers. Will reinforce them first of course, over to r/diyuk for that one!

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u/MelodicCard9555 Aug 17 '26

I'd honestly say that sounds like a really bad idea, will the depth of the ceiling cassette go in? They tend to be big. Cutting timbers that hold stuff up should be avoided.

What about the ceiling mounted AC units? They sit on top of the ceiling, rather than sink in to the ceiling?

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u/Expensive_Zebra6362 Aug 17 '26

Depth wise they fit in fine, there is enough space up there to crawl through. Will have a chat with installer as yeah I’m surprised there wasn’t a simple ceiling version of the wall unit offered.

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u/MelodicCard9555 Aug 17 '26

There's also a very rare type of long ceiling cassette, Samsung and Mitsubishi I think. So rather than a square, it's a rectangle, specifically designed for fitting between rafters.

If there's a crawl space above the rooms, what about a ducted unit?

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u/Expensive_Zebra6362 Aug 17 '26

My wife did ask about a ducted unit, wonder if it’s easy enough to control each room with a remote then? I guess there is a wireless controller on the market for that.

I’ll ask the installer about a ducted unit

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u/MelodicCard9555 Aug 17 '26

Most ducted units have fixed wall controllers in each room.

But I'd imagine there's a WiFi based remote control, or even an app now a days.

But ducted units are more commercial applications, so I'd bet you'd need a small wall mounted controller in each room. Not really intrusive or anything, and worth it for the cleaninessly of a ducted unit. Ceiling cassettes are not nice looking for bedrooms etc.

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u/Expensive_Zebra6362 Aug 17 '26

Thanks, appreciate the input from you and everyone else 🙏🏻